master server down - lvs cluster default to emergency server

[Alois Treindl]

Hello

I have a small question:

My LVS NAT cluster consists of several http servers, and one mysql
database server.

I understand that I can configure piranha via lvs.cf to make healt 
checks on the  httpd service as well as on the mysql server

Now, if the database server is down, all web servers become
dysfunctional, as they cannot provide application data anymore.

I need to announce to all web users a 'server down' page.
I do this by directing all http/https requests to an emergency server.

It's apache server is configured to show the same emergence page for any
URL it receives. The emergency apache server runs on the router/director
itself.

How con I configure piranha lvs.cf in such a way, that, if the mysql 
health check fails, it redirects all http and https request coming into 
the LVS to the emergyency http server?

My healty ipvs configuration looks like this:
${IPVSADM} -A -t $LVS:www -s wlc -p 60
${IPVSADM} -a -t $LVS:www -r w1:www -m -w 2000
${IPVSADM} -a -t $LVS:www -r w5:www -m -w 2000
${IPVSADM} -a -t $LVS:www -r w6:www -m -w 2000
${IPVSADM} -A -t $LVS:https -s wlc
${IPVSADM} -a -t $LVS:https -r w1:https -m -w 1000

my 'sick' configuration (with redirection to the emergency server)
looks like this:
${IPVSADM} -A -t $LVS:www -s rr
${IPVSADM} -a -t $LVS:www -r $WWC:www -m
${IPVSADM} -A -t $LVS:https -s rr
${IPVSADM} -a -t $LVS:https -r $WWC:www -m
where $WWC is the real (external) IP of the director/router

Can piranha do the switch to the 'emergency state'?

Piranha does not have to turn the servers back on automatically, when 
the database service recovers. In my experience, often some manual work 
is required on the dbms server, before the web service can be resumed.


Alois Treindl
Switzerland